These are some of our favourite sites at Roydon Primary. I have tried to only include the better quality apps here as there are loads available and it is often hard to decide what to buy. There is a post here from Deer class about their favourite apps too.
Multiple wipeout from Primary games has been a favourite for a while now. Select the times tables that you want to practice, then pop all the multiples as quickly as you can. Can you beat your personal best time?
69p 


Toy Shop HD lets you practise your money skills. Can you give the correct amount of coins to pay for toys?
69p 
Pop maths!
Match the sums to the answers. Calculations are fun!
Free 
Maths sumo is a great little game for playing in pairs. It builds quick mental and oral skills as you compete against your partner.
Free

I am Learning is an iphone app that will work on the ipad. You complete some questions then got rewarded with a game.
£1.49 
Undersea maths.
Complete the sums to solve the puzzle.
Free 
Super 7 Can you make 7? Can you stop it making numbers more than 7? Speedy problem solving and quick addition skills needed!
69p 
Motion math zoom is a stretchable number line that helps children learn the relationship between numbers. Free Early Bird Practise your times tables for 69p £1.49 Does what it says on the tin! Created by Sherston software. Beluga maths Free Recommended by @traveller_123, you can find out more here and I will review it asap. On first look I am drawn to the visual side of it. There is a x table app too. 
Epic Maths
Nice little maths app for 69p
Mcgraw Hill apps I got this when they were free and they are nice little apps for maths calculation skills, though be aware they are American so the sums are columns not linear. Multiplication Addition Sail through math Monster squeeze Fractions Free Identify the fractions shown by the pizza  as simple as that! 
Grand Prix multiplication
Well I am an F1 fan!! This app does what it says on the tin. 69p
Problem solving This first app asks you to make 10. It starts of easier, then requires a bit of logical / strategical thinking as you go through the levels. I got this one free through apps gone free. Countdown numbers game does what it says on the tin, though at £1.99. Numbers is another good app that asks you to create numbers in a kind of countdown style. You can only use the numbers given and symbols once. The adverts may bug you though ... 